Printers are well known and are used to print documents onto loose, single sheets of paper. Such documents can include, for example, preprinted forms that are 8½″×11″ or A4 as well as narrower documents such as receipts, checks, etc. For ease of discussion, the terms document and sheet are used interchangeably. A document can be a blank sheet or a pre-printed sheet. Alternatively, a document can be a multi-part or multi-ply form, with or without carbon paper. A sheet is typically of paper but is not limited to paper.
Document feeder devices are typically used to feed sheets through a printer. FIG. 1 is a top-view diagram of a conventional document feeder device 50 of a printer 51. The document feeder device 50 advances a sheet 52 along a paper path in a slot 58. The document feeder device 50 includes a set of rollers 62–68 disposed around a pair of roller shafts 70 and 72. The ends of the roller shafts 70 and 72 are directly connected to and supported by bearings 74, 76, 82, and 84, respectively, which are connected to and supported by frame supports 78, 80, 86, and 88, respectively. The sheet 52 is placed parallel to the shafts 70 and 72 and between the rollers 62–68. The roller shafts 70 and 72 rotate in opposite directions to advance the sheet 52 through the printer 51.
The problem with the conventional document feeder device 50 is that is difficult to provide an adequately rigid and stable mounting surface for the roller shafts 70 and 72. A slight movement of one of the roller shafts 70 and 72 causes a substantial misalignment between the rollers 62 and 66 and/or between the rollers 64 and 68. Unfortunately, there is not a way to bridge a support across the front and main portions 54 and 56 without obstructing the paper path.
One conventional solution to the problem is to make the overall printer frame, including the frame supports 78, 80, 86, and 88 as rigid as possible. Accordingly, it would be necessary to keep a tight tolerance of multiple parts associated with the frame supports 78–88. However, doing so increases the cost of production by requiring additional frame hardware and/or more rigid frame hardware.
Accordingly, what is needed is an improved system and method for keeping the rollers of a printer aligned to more reliably feed documents through the printer. The system and method should be cost effective and easily implemented in existing designs. The present invention addresses such a need.